1. Field of the Invention
The present invention relates to a pneumatic tire, and more particularly to a bead structure being capable of reducing the weight of the bead portions without deteriorating the bead durability.
In pneumatic tires used under relatively heavy loads such as heavy duty tires for trucks and buses, light truck tires and the like, a large volume of bead apex rubber is disposed between a carcass ply turnup portion and a main portion to increase the bead rigidity and thereby to decrease deformation of the tire under heavy loads.
2. Background of the Prior Art
Recently, in order to decrease tire weight, the bead structures have been reexamined, and many efforts have been made to decrease the weight of the bead portions by decreasing the volume of bead apex rubber.
In such tires of which the bead apex rubber is very small, the movements and bending deformation of the carcass plies under loads are relatively large. Therefore, as the tension of the carcass cords is large and a large stress concentrates on contacting points with the bead core, the carcass cords are liable to be cut.